BlueTracker

Visions of N’Zoth opens the doors on Heroic Difficulty Operation: Mechagon, giving players the opportunity to experience this mechanically marvelous dungeon in two parts—the Junkyard and the Workshop.

Read more here.

Yes. For those who didn’t get to (or chose not to) run through this dungeon in Mythic, going through it in Heroic will count toward unlocking the mecha-gnomes.